1. Field of the Invention
The present invention relates to a queuing apparatus and method for avoiding address collision of data in a plurality of frames, and more particularly, to a queuing apparatus and method for avoiding address collision in a data communications network.
2. Background
The telecommunications industry has developed systems for transmission and reception of digital data signals organized in a plurality of temporal frames, such as synchronous optical network (SONET) frames. The SONET is an industry-standard optical network that is used for the transmission of various types of communication signals, such as telephony and video signals. The SONET frames are organized in a plurality of superframes, each superframe having a duration of 1 ms and consists of 8 frames each having a duration of 125 .mu.s. Digital data originating from a plurality of channels may be multiplexed by using the technique of time division multiplexing (TDM) and formatted into a plurality of asynchronous transfer mode (ATM) cells for transmission over a SONET physical layer interface. A SONET frame may consist of a plurality of ATM cells including at least some of the ATM cells which contain TDM data that have been formatted into the cells. In order to demultiplex the TDM data in the cells upon reception, it is important that the cells be queued in the receive direction to allow for frame realignment and reformatting such that the queued cells can be properly received into the isochronous environment of the SONET receiver without data collision. Since multiple physical layer devices usually share the same receive interface, it is important that separate receive queues be maintained for the interfaces receiving the respective frames. Various factors, such as fiber loop delays which may vary by more than one SONET frame duration and may differ from interface to interface, may contribute to the address collision of data in the TDM cells of different frames at the receive interface from time to time. Therefore, there is a need for a queuing apparatus and method to avoid the address collision of data in different frames by repositioning the start of the frames in a temporal sequence.